(a) Field of the Invention
The invention relates to a transflective liquid crystal display and, more particularly, relates to a transflective liquid crystal display having optimum gamma curves for a transmissive area and a reflective area of the transflective liquid crystal display.
(b) Description of the Related Art
FIG. 1A partially shows a schematic cross-section of a conventional transflective liquid crystal display. Referring to FIG. 1A, the transflective liquid crystal display 90 includes a color filter substrate 912, an array substrate 914 and a liquid crystal layer 916. The color filter substrate 912 and the array substrate 914 are opposite each other. The liquid crystal layer 916 is interposed between the substrates 912 and 914 and has negative dielectric anisotropy, so that the liquid crystal molecules are in vertical alignment when a voltage is not applied thereto. Switching devices such as thin-film transistors (not shown), transparent pixel electrodes 922 and reflective pixel electrodes 923 are formed on a transparent substrate 928 of the array substrate 914. In the color filter substrate 912, a color filter layer 930 is formed on a transparent substrate 926, and a common electrode 924 is formed on the color filter layer 930. The color filter layer 930 includes a black matrix layer 934 and filter traces 932.
In the conventional transflective liquid crystal display 90, only a single gap is formed between the color filter substrate 912 and the array substrate 914. Hence, it is not easy to adjust the gamma values for a transmissive area and a reflective area to approach a standard gamma curve 2.2, and therefore resulting in inferior image quality. In a conventional design, a display having an organic layer is used to solve the above problem. FIG. 1B partially shows a schematic cross-section of another conventional transflective liquid crystal display. The conventional transflective liquid crystal display 90B is similar to the transflective liquid crystal display 90 shown in FIG. 1A, except the transflective liquid crystal display 90B further includes an organic layer 924 between the reflective pixel electrode 923 and transparent substrate 928. The formation of organic layer 924 enables the transflective liquid crystal display 90B to have two different gaps between the color filter substrate 912 and the array substrate 914. Compared with the transflective liquid crystal display 90, in the transflective liquid crystal display 90B, the light 12 passing through the liquid crystal layer 916 in the reflective area follows a light path similar to the light path of the light I1 passing through the liquid crystal layer 916 in the transmissive area. Accordingly, the gamma values for the transmissive area and the reflective area of the transflective liquid crystal display 90B are relatively easy to be adjusted to approach a standard gamma curve 2.2.
In addition, when a user watches a vertically-aligned LCD at a large viewing angle, a color washout phenomenon is often observed where the skin color tends to appear in pale blue or white. In addition, when a conventional liquid crystal display is touched by a finger of a user, the orientations of liquid crystal molecules become disordered to cause a white or black fingerprint, which is often referred to as fingerprint mura. In the conventional liquid crystal display, it takes a relatively long time for the liquid crystal molecules to recover from the disordered state, so the fingerprint mura is often observed by human eyes.